Journal Articles in Robotics/Dynamics Area

Title: Behaviors for Physical Cooperation Between Robots for Mobility Improvement

Authors: Deshpande, A. D., and Luntz, J. E.

Abstract:

A team of small, low-cost robots instead of a single large, complex robot is useful in operations such as search and rescue, urban exploration etc. However, the performance of such a team is limited due to the restricted mobility of the team members. This paper presents the results obtained toward the goal of enhancing mobility of a team of mobile robots by physical cooperation among the robots. Our focus is on the development of the low level system components. Recognizing that small robots need to overcome discrete obstacles, we develop specific analytical maneuvers to negotiate each obstacle where a maneuver is built from a sequence of fundamental cooperative behaviors. The overall goal is to design the mechanisms and the behaviors for mobile robot cooperation such that they can be employed on existing mobile robots with minimal modifications and where interaction takes place via an un-actuated link through the use of ground forces rather than an actuated link. We analyze the cooperative lift behavior and demonstrate that useful maneuvers such a gap crossing can be built using this behavior.

It is shown, with a static analysis, that requirements on ground friction and wheel torques set fundamental limits for physical cooperation. A novel connecting link design is proposed that can change the system configuration with no additional actuators. Using the design guidelines based on static analysis we have developed simple and low cost hardware to illustrate cooperative gap crossing with two robots. We have developed a complete dynamic model of two-robot cooperation which leads to control design. A decentralized control architecture is designed for the two-robot system, where each robot controls its own state with no information about the state of the other robot thus avoiding the need of continuous communication between the two robots. Simulation and hardware results demonstrate a successful implementation with the gap crossing example. We have analytically proved that robot dynamics can be used to reduce the friction requirements and have demonstrated, with simulations, the implementation of this idea for the cooperative lifting behavior.

Index Terms: mobile robots, mobility, cooperation